I. Field of the Invention
The present invention relates generally to mechanical transfer mechanisms and, more particularly, to such a mechanism with automatic accumulating means.
II. Description of the Prior Art
Conveyors and conveyor systems are currently oftentimes employed in manufacturing plants and facilities for transporting parts or workpieces throughout the manufacturing plant. In one type of conveyor system, the parts or workpieces are longitudinally slidably supported along a conveyor track and incrementally moved from one work station to the next by a reciprocating series of pusher dogs. These dogs conventionally are pivotal between an upper workpiece engaging position during its forward motion and a lower or workpiece clearing position during retraction of the pusher dogs from their most forward to their most rearward position. Otherwise, the pusher dogs would interfere with the workpieces or parts positioned upon the track during their rearward movement or retraction.
Conventionally, the pusher dogs are extended and retracted by any of a number of reciprocal drive means so that the pusher dogs all move in unison with each other for a single conveyor system. Consequently, the parts or workpieces positioned upon the conveyor track are likewise incrementally moved from one work station and to the next forward work station in unison with each other. One disadvantage, however, of the conveyor systems of this type is that a vacant space on the conveyor track caused by the absence of a workpiece at that work station will be moved along the conveyor track in unison with the parts or workpiece. These vacant spaces along the conveyor track, of course, are disadvantageous since the conveyor system is not used at its maximum capability. Moreover, the lack of a workpiece or part at a designated work station in predetermined intervals can cause work interruptions and even a stoppage of the entire manufacturing line.
There have, however, been previously known accumulating conveyor systems in which the pusher dogs are selectively actuated or moved to their upper work engaging position in dependence upon the absence of a workpiece or part from a predetermined work station. One conveyor system of this type is disclosed in U.S. Pat. No. 3,557,943 which issued on Jan. 26, 1971, to Richard Broser.
In the Broser patent, an elongated detector arm is pivotally mounted to the conveyor frame and is movable between an actuating and nonactuating position. In the actuating position, one end of the detector arm is positioned above the conveyor track at one work station due to a lack of a workpiece at that work station while the other end of the detector arm engages and pivots upwardly the next rearwardly pusher dog. The pivoting of the pusher dog to its workpiece engaging position in turn pivots all pusher dogs rearwardly of it to their upper workpiece engaging position. Conversely, a workpiece positioned at the forward work station will pivot the detector arm to its lower or nonactuating position in which case the next rearwardly pusher dog remains in its lower or workpiece clearing position.
One disadvantage of the Broser device, however, is that the detector arm must, of necessity, extend for the entire length between adjacent work stations, i.e. from the forward work station and to the next rearward work station. Therefore, when the work stations are positioned relatively far apart from each other, the detector arms become equally as long, bulky and expensive in construction.